Roll 25 Alpa Alu is a glass-fibre/aluminium reinforced bituminous air and vapour control layer (AVCL) with ALPA binder and is used as part of a system to control the movement of air, water vapour and heat leakage from within the building. Suitable for use in bitumen, single ply and liquid warm roof waterproofing systems, particularly in humid and high humidity conditions.